Underground water conduits, either potable water pipes, waste water pipes or sewer pipes, are typically made of rigid materials such as reinforced concrete, cast iron, ductile iron, steel and hard polymers such as PVC, HDPE, etc. that are durable and adapted to resist high internal pressure if required and the weight of the landfill covering them. Underground water pipes provide essential services to the urban population. A network of buried water pipes connected together extends over long distances, spreads out in all directions through lateral connections to provide services to residential home or businesses over a wide area.
One of the underlying problems with existing networks of pipes, especially potable water pipes, is that many were made and installed long ago and due to the old age of the pipes, as well as the materials used to make them, many pipes have begun to deteriorate, deform, or have damaged areas. The deformed or damaged areas create weak spots, which may allow water to leak out, roots, and dirt to infiltrate the pipes system and lead to the eventual collapse of the pipes which need to be repaired or replaced.
Replacing older networks of underground water conduits with new ones is unrealistic because of the sheer magnitude of the work that would be involved. However, repairing and rehabilitating existing water networks without the need to excavate represents a feasible alternative. Methods exist for repairing the walls of pipes and other conduits. One such method involves the use of a tubular liner impregnated with a cured-in-place resinous material, referred to as cured-in-place pipe (CIPP) which re-lines the inner walls of the conduit or pipe to repair the network of conduits or pipe. The liner is impregnated with a resin capable of curing and hardening to form a new inner wall for the aging or damaged pipes. The CIPP liner is placed in the pipe, and pressurized water is introduced inside the liner to press the liner against the pipe wall. The resin is allowed to cure and harden, thereby creating a new sealed interior pipe wall.
However, networks of underground pipes typically comprise main pipes and a series of lateral pipes connected to the main pipes via various types of connections such as T-connections, Y-connections or cross branch connections for example. When the tubular CIPP liner is installed into one of the pipes to be relined, the tubular liner ends up covering the lateral openings of the T-connections, Y-connections or cross branch connections. Once the resin of the tubular CIPP liner has cured and hardened, the lateral opening of the connections must be re-opened by cutting out the tubular CIPP liner blocking the lateral opening using a robot having a specifically designed cutting tool. In practice, when pressurized water is introduced and the tubular CIPP liner is pressed against the lateral opening of the connections, the liner expands inside the opening of the branches of the connections to form a blister and the resin seeps into the branches of the connections before it has time to cure thereby soiling the inner walls of the various branches of the connections. Once cured, the thus formed blister and hardened resin splattered inside the branches of the connections must be removed and this task is difficult and time consuming with a robot operating the cutting tool.
Therefore, there is a need for a method and apparatus for repairing and rehabilitating underground conduits or pipes having one or more lateral opening using a tubular CIPP liner which prevents blistering of the tubular CIPP liner inside a lateral branches of a connection and prevents uncured resin from seeping and splattering inside the lateral branches of the connection.